As of today, more than a year after Microsoft stopped updating XP, they also stopped shipping the Anti-Malware updates through Windows update.
Does it mean you should upgrade your players? Yes and no, it's a cost/benefit question as always. You should still be pretty safe if your players are in a controlled environment and the Windows Firewall is on. Also there's cheap or even free 3rd party antivirus programs you could install.
However, if you have the time and resources, upgrade to a newer OS. We even support Windows 10 so there should be no issues upgrading the player to a newer OS.
More info here for those that are interested.